1. Field of the Invention
This invention generally relates to ultraviolet discharge lamp apparatuses and, more specifically, to ultraviolet discharge lamp apparatuses having optical filters which attenuate visible light and methods of operating such apparatuses.
2. Description of the Related Art
The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section.
Discharge lamps are used in a variety of applications to generate ultraviolet (UV) light, including but not limited to polymer curing, food sterilization, fluid and object disinfection, and room/area decontamination. For example, it is known that UV irradiation in the spectrum between approximately 200 nm and approximately 320 nm is effective in deactivating and, in some cases, killing microorganisms, giving reason to the use of ultraviolet light technology for disinfecting and/or sterilizing items. In general, discharge lamps refer to lamps which generate light by means of an internal electrical discharge between electrodes in a gas. The electrical discharge creates a plasma which supplies radiant light. In some instances, such as in mercury-vapor lamps, the light generated is continuous once the lamp is triggered. Other configurations of discharge lamps, which are often referred to as flashtubes or flashlamps, generate light for very short durations. Such discharge lamps are sometimes used to supply recurrent pulses of light and, thus, are sometimes referred to as pulsed light sources. A commonly used flashlamp is a xenon flashtube.
Although different types of discharge lamps have been investigated to provide UV light for different applications, little has been done to improve the efficiency of the ultraviolet light generated in apparatuses, particularly with respect to the propagation of the ultraviolet light (i.e., distance and angle of incidence on a target object). A reason for such a lack of advancement is that many apparatuses having discharge lamps, such as food sterilization and single object disinfection devices, are configured to treat items placed in close proximity and in direct alignment with the lamp and, thus, little or no improvement in efficiency of the UV light may be realized by altering its propagation. Furthermore, room/area decontamination systems are specifically designed to disperse light over a vast area and, thus, altering UV propagation from a system may hinder such an objective. In addition, many apparatuses with discharge lamps are limited in application and versatility. For instance, many food sterilization and single object disinfection devices are self-contained apparatuses and are configured for treatment of specific items and, thus, do not generally include features which improve the versatility of the systems for treatment for other items or use in other applications. Furthermore, some apparatuses require time consuming and/or cumbersome provisions in order to protect a user from harm. For example, pulsed ultraviolet light technology generally utilizes xenon flashlamps which generate pulses of a broad spectrum of light from deep ultraviolet to infrared, including very bright and intense visible light. Exposure of the visible light and the ultraviolet light may be harmful and, thus, provisions such as containing the pulsed light within the confines of the apparatus or shielding windows of a room in which a room decontamination unit is used may be needed.
Accordingly, it would be beneficial to develop ultraviolet discharge lamp apparatuses having features which improve their utilization, including but not limited to features which improve the efficiency of the ultraviolet light generated, increase the versatility of the apparatuses, and reduce and/or eliminate time consuming and cumbersome provisions that are required by conventional systems.